.\"	$OpenBSD: inet6.4,v 1.33 2014/01/21 03:15:46 schwarze Exp $
.\"	$KAME: inet6.4,v 1.19 2000/11/24 10:13:18 itojun Exp $
.\"
.\" Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
.\" All rights reserved.
.\"
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.\" modification, are permitted provided that the following conditions
.\" are met:
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.\" SUCH DAMAGE.
.\"
.Dd $Mdocdate: January 21 2014 $
.Dt INET6 4
.Os
.Sh NAME
.Nm inet6
.Nd Internet protocol version 6 family
.Sh SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <netinet/in.h>
.Sh DESCRIPTION
The
.Nm
family is an updated version of the
.Xr inet 4
family.
While
.Xr inet 4
implements Internet Protocol version 4,
.Nm
implements Internet Protocol version 6.
.Pp
The
.Nm
family is comprised of the
Internet Protocol version 6
.Pq Tn IPv6
network protocol, Internet Control
Message Protocol version 6
.Pq Tn ICMPv6 ,
Transmission Control Protocol
.Pq Tn TCP ,
and User Datagram Protocol
.Pq Tn UDP .
.Tn TCP
is used to support the
.Dv SOCK_STREAM
abstraction while
.Tn UDP
is used to support the
.Dv SOCK_DGRAM
abstraction.
Note that
.Tn TCP
and
.Tn UDP
are common to
.Xr inet 4
and
.Nm inet6 .
A raw interface to
.Tn IPv6
is available
by creating an Internet socket of type
.Dv SOCK_RAW .
The
.Tn ICMPv6
message protocol is accessible from a raw socket.
.\" .Pp
.\" The 128-bit IPv6 address contains both network and host parts.
.\" However, direct examination of addresses is discouraged.
.\" For those programs which absolutely need to break addresses
.\" into their component parts, the following
.\" .Xr ioctl 2
.\" commands are provided for a datagram socket in the
.\" .Nm
.\" domain; they have the same form as the
.\" .Dv SIOCIFADDR
.\" command (see
.\" .Xr intro 4 ) .
.\" .Pp
.\" .Bl -tag -width SIOCSIFNETMASK
.\" .It Dv SIOCSIFNETMASK
.\" Set interface network mask.
.\" The network mask defines the network part of the address;
.\" if it contains more of the address than the address type would indicate,
.\" then subnets are in use.
.\" .It Dv SIOCGIFNETMASK
.\" Get interface network mask.
.\" .El
.Pp
For security reasons,
.Ox
does not route IPv4 traffic to an
.Dv AF_INET6
socket,
and does not support IPv4 mapped addresses,
where IPv4 traffic is seen as if it comes from an IPv6 address like
.Li ::ffff:10.1.1.1 .
Where both IPv4 and IPv6 traffic need to be accepted, listen on two sockets.
.Sh ADDRESSING
IPv6 addresses are 16 byte quantities, stored in network standard byteorder.
The include file
.In netinet/in.h
defines this address
as a discriminated union.
.Pp
Sockets bound to the
.Nm
family utilize the following addressing structure:
.Bd -literal -offset indent
struct sockaddr_in6 {
	u_int8_t	sin6_len;
	sa_family_t	sin6_family;
	in_port_t	sin6_port;
	u_int32_t	sin6_flowinfo;
	struct in6_addr	sin6_addr;
	u_int32_t	sin6_scope_id;
};
.Ed
.Pp
Sockets may be created with the local address
.Dq Dv ::
.Po
which is equal to IPv6 address
.Dv 0:0:0:0:0:0:0:0
.Pc
to effect
.Dq wildcard
matching on incoming messages.
.Pp
The IPv6 specification defines scoped address,
like link-local or site-local address.
A scoped address is ambiguous to the kernel,
if it is specified without a scope identifier.
To manipulate scoped addresses properly from userland,
programs must use the advanced API defined in RFC 3542.
A compact description of the advanced API is available in
.Xr ip6 4 .
If scoped addresses are specified without explicit scope,
the kernel may raise an error.
Note that scoped addresses are not for daily use at this moment,
both from a specification and an implementation point of view.
.Pp
KAME implementation supports extended numeric IPv6 address notation
for link-local addresses,
like
.Dq Li fe80::1%de0
to specify
.Do
.Li fe80::1
on
.Li de0
interface
.Dc .
The notation is supported by
.Xr getaddrinfo 3
and
.Xr getnameinfo 3 .
Some normal userland programs, such as
.Xr telnet 1
or
.Xr ftp 1 ,
are able to use the notation.
With special programs
like
.Xr ping6 8 ,
an outgoing interface can be specified with an extra command line option
to disambiguate scoped addresses.
.Pp
Scoped addresses are handled specially in the kernel.
In the kernel structures like routing tables or interface structure,
scoped addresses will have their interface index embedded into the address.
Therefore,
the address on some of the kernel structure is not the same as that on the wire.
The embedded index will become visible on
.Dv PF_ROUTE
socket, kernel memory accesses via
.Xr kvm 3
and some other occasions.
HOWEVER, users should never use the embedded form.
For details please consult
.Lk http://www.kame.net/dev/cvsweb2.cgi/kame/IMPLEMENTATION .
Note that the above URL describes the situation with the latest KAME tree,
not the
.Ox
tree.
.Sh SEE ALSO
.Xr ioctl 2 ,
.Xr socket 2 ,
.Xr sysctl 3 ,
.Xr icmp6 4 ,
.Xr intro 4 ,
.Xr ip6 4 ,
.Xr tcp 4 ,
.Xr udp 4
.Sh STANDARDS
.Rs
.%A Tatsuya Jinmei
.%A Atsushi Onoe
.%D June 2000
.%N draft-ietf-ipngwg-scopedaddr-format-02.txt
.%O work in progress material
.%R internet draft
.%T "An Extension of Format for IPv6 Scoped Addresses"
.Re
.Pp
.Rs
.%A R. Gilligan
.%A S. Thomson
.%A J. Bound
.%A J. McCann
.%A W. Stevens
.%D February 2003
.%R RFC 3493
.%T Basic Socket Interface Extensions for Ipv6
.Re
.Pp
.Rs
.%A W. Stevens
.%A M. Thomas
.%A E. Nordmark
.%A T. Jinmei
.%D May 2003
.%R RFC 3542
.%T Advanced Sockets Application Programming Interface (API) for IPv6
.Re
.Sh HISTORY
The implementation described herein appeared in WIDE/KAME project.
.Sh BUGS
The IPv6 support is subject to change as the Internet protocols develop.
Users should not depend on details of the current implementation,
but rather the services exported.
.Pp
.Dq Version independent
code should be implemented as much as possible in order to support both
.Xr inet 4
and
.Nm inet6 .
